The identification of the development of nanostructures and biosystems through various fluorescent markers has the potential to lead to the technical difficulties of labeling and the false results of fluorescent markers. Therefore, research is being conducted through the detection of Raman signal inherent to the substance without labeling.
However, there is a practical limit to the detection of Raman signal because it has a very small intensity compared to fluorescence.
To unravel the issue, the researches on SERS sensors using gold or silver nanostructure are actively underway.
This is due to the use of surface Plasmon in the metal structure confined to nanometer size, that is, Localized Surface Plasmon Resonance (LSPR). Biosensor applications such as detection of a very small amount of biomolecules by Raman signal amplification will be possible when resonance energy is irradiated for metal nanostructure. In addition, the optimal SERS sensor structure enables Raman enhancement of 108 or more, enabling single molecule detection.
Various studies have been reported to maximize the SERS signal: synthesis of various types of nanoparticles [Jianping Xie, Jim Yang Lee, and Daniel I. C. Wang, 2007, Chem. Mater., 19, 2823-2830], the strong electric field between nanoparticles under LSPR [Ping-Ji Huang, et al, 2009, Adv. funct. Mater., 19, 242-248], a stimulus-responsive polymer to control the nanogap-distance between nanoparticles [Laura Rodriguez-Lorenzo, et al. 2009, J. AM. CHEM. SOC, 131, 4616-4618]. Therefore, the substrate for the SERS sensor capable of high sensitivity biosensing and chemical sensing with only a small amount of sample can be considered.
However, a method for evaluating whether or not such a substrate for an SERS sensor is well manufactured to have excellent performance is not known, and a simple and systematic method for evaluating a substrate for an SERS sensor is needed.